The present invention relates to a transmission for a track-laying vehicle and more particularly relates to a parallel cross shaft transmission including constant-mesh spur gear sets wherein a coupling or clutch is associated with each set for selectively establishing a driving connection between cross shafts associated with the set.
The prior art includes various crawler tractor transmissions including bevel gear reverser sections which are coupled to speed change sections including cross shafts carrying selectively engagable spur gear sets. Specifically in U.S. Pat. No. 2,746,319 issued to Gates on May 22, 1956, there is disclosed a reverser section which includes a single output shaft selectively coupled to an input shaft of the speed change section through means of a pair of selectively engageable spur gear sets. In addition to the speed change section, the Gates patent discloses a steering section including a differential gear set which operates to effect power-turning by causing one track to be driven at a slower speed than the other.
U.S. Pat. No. 3,056,310 issued to Ruf on Oct. 2, 1962, discloses a transmission including a reversing section coupled to two output shafts such that both output shafts may selectively be driven in the same direction or in opposite directions, the latter condition being effected for driving one of the vehicle tracks in one direction and the other vehicle track in the opposite direction to accomplish spin-turning.
U.S. Pat. No. 3,535,954 issued on Oct. 27, 1970 to Chambers et al discloses a reversing section for selectively driving a single output shaft in opposite directions, the output shaft being coupled to a pair of final drive-connected shafts through means of respective spur gear sets forming parts of planetary gearing carried by the output and final drive-connected shafts. The planetary gear sets of the transmission are selectively operable to effect steering conditions whereby the vehicle may be power-turned with one track driving slower than the other track, pivot-turned with one track dead and the other rotating or spin turned with one track rotating forwardly and the other rotating reversely. While the transmission illustrated in this patent operates to effect three different modes of steering and several ground speeds in forward or reverse, the means for accomplishing the same includes relatively elaborate planetary gear sets which are relatively costly.